Some years ago I wrote a GUI editor named FreeForm in Liberty BASIC. I did this to show my users that they could build interesting software. FreeForm comes with Liberty BASIC, including source code. The Liberty BASIC editor permits users to add tools to the Run menu, so FreeForm comes as a tool on that menu when Liberty BASIC is installed.
I haven't worked on updating FreeForm in several years, but that hasn't stopped it from growing and becoming better. The Liberty BASIC community took over development and they've produced several versions, and some of these have been included with Liberty BASIC. Right now they're working on a whole new version, which I hope may be included in Liberty BASIC v4.03.
Other really cool tools that LB programmers have created have been code formatters, lint tools, and even whole IDE's. Brent Thorn is working on a complete IDE for Liberty BASIC written in Liberty BASIC called ViviFire, which includes a BASIC scripting language so that users can extend the IDE in itself. Extra cool!